In a small bowl, whisk together 2 cups buttermilk and 1 teaspoon sriracha until smooth.
Place chicken tenders (about 2 lb) in a gallon-size resealable bag or 1‑gallon container and pour in the buttermilk mixture to coat. Seal and refrigerate for 1 hour.
In a large shallow bowl, whisk together 2 cups all-purpose flour, 2 tablespoons cornstarch, 2 teaspoons kosher salt, 1 teaspoon cracked black pepper, 1 teaspoon onion powder, 1/2 teaspoon baking soda, and 1/2 teaspoon smoked paprika.
In a medium shallow bowl, beat 4 large eggs with a fork until combined.
Pour about 6 cups vegetable oil into a 5–6 quart Dutch oven and heat over medium-high until it reaches 350°F on a thermometer.
Line a baking dish or platter with paper towels for draining the cooked tenders.
Using tongs, remove one marinated tender at a time, dredge in the flour mixture, then dip in the beaten eggs, and dredge again in the flour mixture to fully coat. Repeat with remaining tenders and discard the used marinade.
Carefully add 3–4 tenders to the hot oil without crowding and fry for 4–5 minutes, turning if needed, until golden brown and cooked through.
Transfer cooked tenders to the paper towel–lined dish to drain. Continue frying remaining tenders, keeping an eye on oil temperature and adjusting heat to maintain 350°F.
Serve the chicken tenders hot with your favorite dipping sauce or white gravy.